如何使用zlib压缩缓冲区？ [英] How to compress a buffer with zlib?

问题描述

zlib网站上有一个使用示例： http://www.zlib.net/zlib_how.html

但是在示例中，他们正在压缩文件。我想压缩存储在内存中缓冲区中的二进制数据。我不想将压缩缓冲区保存到磁盘。

基本上这里是我的缓冲区：

  fIplImageHeader-> imageData =（char *）imageIn-> getFrame（）; 
  

如何使用zlib压缩？

解决方案

这是一个用zlib包装缓冲区的示例，将压缩内容保存在向量中。

  void compress_memory（void * in_data，size_t in_data_size，std :: vector< uint8_t> ; out_data）
 {
 std :: vector< uint8_t>缓冲; 
 
 const size_t BUFSIZE = 128 * 1024; 
 uint8_t temp_buffer [BUFSIZE]; 
 
 z_stream strm; 
 strm.zalloc = 0; 
 strm.zfree = 0; 
 strm.next_in = reinterpret_cast< uint8_t *>（in_data）; 
 strm.avail_in = in_data_size; 
 strm.next_out = temp_buffer; 
 strm.avail_out = BUFSIZE; 
 
 deflateInit（& strm，Z_BEST_COMPRESSION）; 
 
 while（strm.avail_in！= 0）
 {
 int res = deflate（& strm，Z_NO_FLUSH）; 
 assert（res == Z_OK）; 
 if（strm.avail_out == 0）
 {
 buffer.insert（buffer.end（），temp_buffer，temp_buffer + BUFSIZE）; 
 strm.next_out = temp_buffer; 
 strm.avail_out = BUFSIZE; 
} 
} 
 
 int deflate_res = Z_OK; 
 while（deflate_res == Z_OK）
 {
 if（strm.avail_out == 0）
 {
 buffer.insert（buffer.end（），temp_buffer， temp_buffer + BUFSIZE）; 
 strm.next_out = temp_buffer; 
 strm.avail_out = BUFSIZE; 
} 
 deflate_res = deflate（& strm，Z_FINISH）; 
} 
 
 assert（deflate_res == Z_STREAM_END）; 
 buffer.insert（buffer.end（），temp_buffer，temp_buffer + BUFSIZE  -  strm.avail_out）; 
 deflateEnd（& strm）; 
 
 out_data.swap（buffer）; 
} 
  

There is a usage example at the zlib website: http://www.zlib.net/zlib_how.html

However in the example they are compressing a file. I would like to compress a binary data stored in a buffer in memory. I don't want to save the compressed buffer to disk either.

Basically here is my buffer:

fIplImageHeader->imageData = (char*)imageIn->getFrame();

How can I compress it with zlib?

I would appreciate some code example of how to do that.

解决方案

This is an example to pack a buffer with zlib and save the compressed contents in a vector.

void compress_memory(void *in_data, size_t in_data_size, std::vector<uint8_t> &out_data)
{
 std::vector<uint8_t> buffer;

 const size_t BUFSIZE = 128 * 1024;
 uint8_t temp_buffer[BUFSIZE];

 z_stream strm;
 strm.zalloc = 0;
 strm.zfree = 0;
 strm.next_in = reinterpret_cast<uint8_t *>(in_data);
 strm.avail_in = in_data_size;
 strm.next_out = temp_buffer;
 strm.avail_out = BUFSIZE;

 deflateInit(&strm, Z_BEST_COMPRESSION);

 while (strm.avail_in != 0)
 {
  int res = deflate(&strm, Z_NO_FLUSH);
  assert(res == Z_OK);
  if (strm.avail_out == 0)
  {
   buffer.insert(buffer.end(), temp_buffer, temp_buffer + BUFSIZE);
   strm.next_out = temp_buffer;
   strm.avail_out = BUFSIZE;
  }
 }

 int deflate_res = Z_OK;
 while (deflate_res == Z_OK)
 {
  if (strm.avail_out == 0)
  {
   buffer.insert(buffer.end(), temp_buffer, temp_buffer + BUFSIZE);
   strm.next_out = temp_buffer;
   strm.avail_out = BUFSIZE;
  }
  deflate_res = deflate(&strm, Z_FINISH);
 }

 assert(deflate_res == Z_STREAM_END);
 buffer.insert(buffer.end(), temp_buffer, temp_buffer + BUFSIZE - strm.avail_out);
 deflateEnd(&strm);

 out_data.swap(buffer);
}

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